Porsche's 918 RSR's performance hybrid system relies on this giant flywheel — sitting where a passenger seat should be — to capture and release energy on command. It's a real-life turbo boost button. Here's how it works.



Step 1.) Hit the Brakes!
The driver mashes, feathers or otherwise stomps the middle pedal. Clever electrical stuff starts happening.



Step 2.) Zzzzt!
Two electric motor/generators, each one dedicated to a separate front wheel, kick into reverse—or generating mode—and begin converting the car's forward motion into an electrical current.



Step 3.) The Flywheel Accumulator!
Inside that ominous nuclear-reactor dome resides a carbon-fiber flywheel, which revolves inside a stator. Because the flywheel's in a vacuum (no drag) and been loaded with magnetic material, it acts just like a electric motor/generator. When the current generated during braking reaches the flywheel, it increases the flywheel's rotation speed from an idle state of around 20,000 rpm up to a maximum of 36,000 rpm, in the process storing electrical energy as kinetic energy.



Step 4.) Boost!
Maybe he wants to initiate a pass, or grab some front-wheel traction to quicken his track-out, or just wants to try and preserve fuel incrementally. Whatever the reason, the driver pushes the boost button and hangs on.



Step 5.) The Flywheel Accumulator Again!
The stator converts some of those high flywheel rpms back into electricity. Because energy is conserved (remember physics class) the speed of the flywheel decreases as it gives back some of the electrical energy.



Step 6.) Motors! Go!
The current generated from the flywheel powers those front-wheel motor/generators for an eight-second boost of 150kW (201 hp). The system can also initiate torque vectoring, distributing torque to each of the front wheels as needed to enhance traction.

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